Studies On Controlable Synthesis Of Hierarchical Porous Alumina And Its NaY Zeolite Composites

The heavy qualitative problem of crude oil has become more serious nowadays,zeolites with the sole presence of micropores may impose severe mass-transfer constraints on the rate of catalysed reactions and limit the applications involving bulky molecules.With regard to traditional zeolite granules,the use of inorganic binders for shaping the final zeolite material may partly block access to the zeolite active centers.Hierarchically porous monolith can solve the problems of materials shaping,at the same time,it brings meso/macropore into the micropore,which effectively reduce the reactor pressure drop,increase the material surface area,improve the mass and heat transfer,therefore,the development of newly hierarchically porous catalysts,which produce clean oil from heavy oil,has a significant impact on the energy sustainable using.Hierarchically porous alumina monoliths with micrometer-scaled macropores and mesostructured skeletons were synthesized via a sol-gel process accompanied by phase separation using an aluminum salt?AlCl₃·6H₂O?precursor,water soluble polymer poly?ethylene oxide??PEO?phase separation inducer,and propylene oxide?PO?as gelation agent to control the gelation.Water?H₂O?and absolute ethyl alcohol?EtOH?act as solvents.Imapcts of the molecular weight and additive amount of phase separation inducer PEO,types and additive amount of acid/proton scavenger,the polarityof the solution?water alcohol ratio,H₂O/EtOH?,calcination temperature and time etc synthesis conditions on the preparation of hierarchically porous alumina were discussed detailedly.When the additive amount of PEO?viscosity-averaged molecular weight,Mv:1×10⁶?was 0.09g,the feed ratio of H₂O:EtOH:AlCl₃·6H₂O:PO=12.4:5.28:1:2.99,using a simple method to slow down the solvent evaporation rate during the drying process of wet gel,allows the production of bicontinuous structured macroporous alumina monoliths with macropore size in the range of 0.5²?m.Porous alumina with uniform microstructure and monolithic preserved morphology were controllable synthesized by adjusting the reactants added order to improve the non-uniform structured product arised in the large-scale preparation.Moreover,in the case of ensuring the macroscopic monolithic and microscopic bicontinuous porous structure,triblock copolymers?P123,F127?were added to the synthesis system to adjust the aperture and morphology of mesopores.The controllable synthesized macro-mesoporous alumina monoliths were used as substrates for the construction of hierarchically porous zeolite composites.Seed gel was used as directing agent to prepare NaY zeolite as seed for synthesize zeolite composites.Small-grain NaY zeolite were synthesized by increasing the concentration of the silica source,increasing the seed gel additive amount and extending the ageing time of overall gel.The hierarchically structured FAU/alumina composites with trimodal pores?macropores/mesopores/micropores?were hydrothermally synthesized by seeding and secondary growth method.Macro-mesoporous?-Al₂O₃ and?-Al₂O₃ monoliths obtained at different calcination temperatures were used as substrates.With a preliminary seeding step of sonication-assisted vaccum adsorption,small-grain Na Y seeds,which were generated with seed gel as directing agent,can be anchored to the porous alumina supports,after hydrothermal crystallization reaction,FAU zeolite can grow and deposit on the walls of the hierarchically porous alumina.The effects of the states of the seed,the seeding times,the reactant ratio,the crystallization conditions,the crystallization modes and the seed gel assistant on the properties of the hierarchically porous zeolite composites with two physicochemical featured supports were investigated.The formation process of secondary growth of zeolite seeds on two physicochemical featured supports were believed to be proceeded by the solution-mediated transport mechanism.Zeolite FAU composites with a macro-meso-micropore hierarchy were hydrothermally synthesized by liquid crystallization directing agent?LCDA?induced method.The macro-mesoporous?-Al₂O₃ and?-Al₂O₃ monoliths substrates obtained at different calcination temperatures were crystallized after multi-stage treatments.The effects of the addition of seed gel,the contribution of the substrates aluminum,the reactant ratio,the crystallization conditions and the crystallization modes on the properties of the hierarchically porous zeolite composites with two physicochemical featured supports were investigated.The formation process of LCDA induced method on?-Al₂O₃ and?-Al₂O₃supports were believed to be proceeded by the solid hydrogel-solution mediated transport mechanism and the solution-mediated transport mechanism,respectively.The synthesis methods of monolithic micro-meso-macroporous zeolite/alumina composites in the thesis can be extended to the other substrates with different compositions and pore structures.The resulting monolithic zeolite with trimodal-porous hierarchy shows potential applicability where bulky molecules involved and facile diffusion is required.